"We are very sorry for recent difficulties with Yahoo Mail," Bonforte writes. "Some of our users have not been able to access their mail since 10:27 PM PT on Monday night, due to a hardware problem in one of our mail data centers. The issue has been harder to fix than we originally expected. We have dozens of people working around the clock to bring it to a resolution. We believe our current efforts will restore our users’ access to their inboxes by 3 pm PT today. We’ll post again then on our @YahooMail Twitter handle."

Yahoo first responded yesterday, saying that it was aware of the issue via Twitter.

"We know some of our users are unable to use Yahoo Mail," Yahoo said in a tweet yesterday. "We're on it & trying to restore access in a few hours. Sorry for the inconvenience."